Developing the initial critical mass in place to entice normal consumers to stick with your site is critically important. Naturally I'd recommend reaching out to your existing social circle to generate a base of user content, usage, reviews, and feedback. Beyond those circles, have you considered reaching out to teams abroad to generate activity from their local regions of interest? This could be a great way to build activity from local experts, and avoid any diluted fluff.

Feel free to reach out to me to discuss more, I'd be happy to consult. Also, you may be interested to hear about my most recent epic travel adventure, to run the 2015 Pyongyang, North Korea marathon.

Cheers